1. Technical Field
The present invention relates to a relay connection unit and a junction connector. More particularly, the present invention relates to a relay connection unit and a junction connector that can improve the routing of communication lines and increase reliability within a vehicle-mounted LAN system.
2. Background Art
In recent years, numerous Electronic Control Units (ECUs) have come to be mounted in automobiles, and the number thereof tends to increase. Respective ECUs are interconnected to each other via communication lines to constitute a vehicle-mounted LAN, and are configured to provide a capability of sending and receiving messages among the ECUs. Furthermore, in order to reduce the amount of messages being transmitted via each of the communication lines, a plurality of the communication lines are connected via a relay connection unit to reduce the number of ECUs connected to a single communication line (one segment of the vehicle-mounted LAN). Further, Patent Document 1: Japanese Patent Unexamined Publication JP-A-2006-67543 discloses a configuration of a junction connector which allows a plurality of communication lines to be connected to a single communication line which constitutes a trunk line.
FIG. 11 shows an exemplary vehicle-mounted LAN built using the aforementioned junction connectors. 90A, 90B . . . represent ECUs mounted on a vehicle. 91A, 91B . . . , 92A, 92B . . . represent communication lines made of twisted pair cables which is compliant with a vehicle-mounted LAN standard such as CAN or the like, connecting between the ECUs 90A, 90B . . . 93A and 93B represent the junction connectors. These ECUs 90A, 90B . . . constitute a first segment of the vehicle-mounted LAN that can mutually transmit and receive messages by respective the communication lines 91A and 91B, the junction connector 93A, and a second segment of the vehicle-mounted LAN with the communication lines 92A and 92B, and the junction connector 93B. In the description blow, each of the members 90A, . . . 91A, . . . 92A, . . . 93A, . . . are respectively indicated by the numerals 90, 91, 92, 93 unless specific distinctions are required.
When the vehicle-mounted LAN so-configured is built, by forming each segment accordingly, and by transmitting/receiving messages accordingly through the selection of the communication lines 91, 92, all the ECUs 90 can transmit/receive messages to/from any of the other ECUs 90. Further, by dividing the junction connectors 93 into groups, one for each of logic paths of the ECUs 90, it is possible to suppress the communication load factor in each communication line 91. Each of gateways 94A, 94B is also represented herein by a reference numeral 94 unless a specific distinction is required.
FIG. 12 indicates a configuration of a vehicle-mounted LAN further using the gateways 94A, 94B. That is, by connecting the junction connectors 93 to the gateways 94A, 94B, and connecting between the respective gateways 94A, 94B using a communication line 910 as a trunk line, each of the ECUs 90 may be able to transmit/receive messages to/from all the ECUs 90 just by being connected to the vehicle-mounted LAN, using at least one communication line 91.
When the vehicle-mounted LAN is configured as the above, by placing the gateways 94A, 94B apart from each other, any ECUs 90 may be connected, via the nearest relay connection unit 94, to each of the ECUs 90 constituting the vehicle-mounted LAN. Thus, the length of each communication line 91 may be reduced. Furthermore, the relay connection unit 93 has communication ports to be connected to four communication lines 91 respectively so as to allow the reduction in the number of ECUs 90 connected to one communication port. Thus, it is capable of reducing the amount of messages relayed by the relay connection unit 93 to each of the communication lines 91. Accordingly, it is possible to reduce the communication load factor in each of the communication lines 91. Further, by using the junction connectors of the Patent Document 1, ringing in the communication lines 91 may be prevented so that the length of the communication lines 91 may be increased to that extent.
However, in the vehicle-mounted LAN configured as shown in FIG. 11, the transmission/reception of messages must be enabled by connecting a plurality of communication lines 91, 92 to a single ECU 90. Thus, it requires not only a larger number of communication lines 91, 92 but also requires each ECU 90 to perform separate communications using a plurality of communication lines 91, 92. Furthermore, a plurality of ECUs 90 are directly connected to each of the junction connectors 93A, 93B, and some of the ECUs 90 are connected to both the junction connectors 93A, 93B. Thus, it has been difficult to freely configure the locations of the ECUs 90.
On the other hand, in the vehicle-mounted LAN configured as shown in FIG. 12, there are a large number of ECUs 90 relative to the number of reception connectors provided to the gateways 94 for connecting the communication lines 91. Thus, there has been necessity that a plurality of the ECUs 90 had to be branch-connected to one communication port using a junction connector 93 in a case where all the ECUs 90 cannot be connected to the reception connectors on one-on-one basis. Accordingly, besides the relay connection unit 92, the junction connectors 93A to 93C and communication lines 91L to 91N for connecting between the junction connectors 93A-93C and the gateways 94 have been needed.
Furthermore, the use of the junction connectors 93 described in Patent Document 1 may reduce the ringing in the communication lines 91. However, there is a limit in the lengths of the communication lines 91, 92 connected to the junction connectors 93, making it difficult to freely arrange the locations of the ECUs 90.